Pacemaker leads represent the electrical link between the pulse generator and the heart tissue which is to be excited. These pacemaker leads include single or multiconductors that are connected to an electrode in an electrode assembly at a distal end of a pacing lead. Typically, a terminal member is mounted within a flexure sleeve at the proximal end of the pacing lead and connected to the proximal end of the conductor.
After the electrode assembly is positioned at a desired location within the heart, it is desirable to provide some method for securing the electrode assembly at that location. Mechanical fixation devices are used to firmly anchor the electrodes in the heart. One type of mechanical fixation device used is a corkscrew, or a helix. The helix is extended and screwed into the heart muscle by applying a torque to the other end of the conductor or by rotating the lead itself. Once the lead is inserted into the tissue, the tissue undergoes trauma, and will attempt to repair itself.
Some leads include drug eluting structures proximate the electrodes to deliver therapeutic drugs near the electrode/tissue interface. However, current leads utilize a drug plugs collar to store and control the release of the drugs. However, as leads become smaller, the size of the drug plugs and collars becomes incompatible with the lead size.
There is a need for a body-implantable lead that has a helix for fixation to the wall of the atrium or ventricle of the heart. In addition, there is a need for an active fixation helix that minimizes trauma to the tissue.